Why men should care about their BMI

(Photo by patricia serna)

Few things make men gain weight as quickly as fatherhood — men exercise less, eat terribly, and endure hormonal changes that pack on the pounds (and keep them packed). Still, just because new dads strain the scales doesn't mean they should be nervous about their weight. Weight measurements can only tell guys so much about their health without taking height into account. However, body mass index, or BMI, figures both height and weight in and this can tell fathers far more about the status of their dad bods.

"Being a Dad doesn't change what his BMI should be," laughs Keith Ayoob, a pediatric nutritionist and clinical practitioner. "You want to keep it under 25. Over 25 is considered overweight and over 30 is obese. These numbers hold throughout adulthood, dad or not."

The measurement of BMI was first introduced in the 19th century by Lambert Adolphe Jacques Quetelet, who was a mathematician and not physician. His goal was to develop a quick and easy formula to measure obesity. Part of the reason BMI caught on as a popular indicator of health is that it's easy for anyone to calculate, as long as they know their height and weight. First, a person would multiply how much they weigh in pounds by 703, then divide it by their height in inches squared. If the results are between 18.5 and 25, they're in a healthy range. If their BMI is above 25 then they're overweight. If it's over 30 they're obese. And if it's under 18.5, they might want to start drinking Ensure. Although men tend to have higher BMIs than women, the recommendations are the same for both. Anything between 18.5 and 25 is ideal.

Figuring out your BMI is simple, but it might be a little too simple, some scientists suspect. The biggest criticism of BMI as an overall health indicator is that it does not take into account the difference between muscle and fat. As a result, someone who does not exercise could have a lower BMI than a professional athlete who's the same height yet weighs more, but that doesn't necessarily make them healthier.

That said, for most dads who are not pro-athletes, a BMI over 25 is most likely going to signal a need for some changes, which are going to be hard to make with kids around

"Men don't go through all the changes women do when having kids, but dad's lifestyle will probably change, and that poses challenges, to be sure," Ayoob says. One of these changes includes testosterone levels that decline when men have children, as well as with age.

"We know that higher testosterone levels leads to less weight gain," adds family physician Jeffrey Walden. "So, unfortunately, men in their thirties and forties will have slower metabolic rates overall compared to their 18-year-old self."

However, Ayoob and Waldern agree that dads should worry less about losing testosterone and more about losing sleep. Sleep deprivation increases stress hormones like cortisol in the body, which can lead to junk food cravings and low energy. Cortisol can actually make bodies swell and hold onto fat cells. As much as diet and exercise can help, parents are never going to get their BMIs under control if they're only getting five hours of sleep a night.

The best thing dads can do to offset their sleep loss and weight gain is to create and stick to a schedule that includes both exercise and sleep. Maintaining a schedule will help dads find new opportunities to move around, whether that means going for a run or pushing a stroller. Given the physical requirements of fatherhood, it's possible that dads who exercise will see their BMI go down and their weight stay the same. That's fine. Strength is not a problem.

"Numbers can be helpful, but don't be overly distracted or lose sight of what's important," Walden recommends. "Most fathers want to ensure they remain healthy enough to spend quality time with their kids. Keeping this at the forefront can help them reach their long-term goals."

This article originally appeared on Fatherly. Follow @FatherlyHQ on Twitter.